Luminaire



Jul; 4, 1944. I w, ROLPH I 2,352,801

LUMINAIRE Filed Aug. '7 1945 INVENTOR. Tao/ms W. ROLPH rm/ma PatentedJuly 4, 1944 Application August 7, 194:, Serial no. 491,740

3 Claims.

Thepresent invention relates to luminaires, and is more particularlydirected toward lumi naires designed for use as contact lights forairplane landingnelds.

Contact lights for landing fields are placed alongside the runways justabove the surface of the ground andare for the purpose of providing twoconcentrated beams slightly lessthan 180 to one another and directed ata slight angle above the horizontal, the beamsfrom the opposite sides ofthe runwaybeingvisible to the aviator when locating the runway andlanding.

The present invention relates to improvements in such contact lightswherein all the light control from the concentrated filament lightsource and its reflector is effected by a one-piece annular refractorwhich is of smaller diameter at the top than at the bottom. I

The accompanying drawing shows, for purposes of illustrating the presentinvention, an embodiment in which the invention may take form, it beingunderstood that the drawing is illustrative of the invention rather thanlimiting the same.

In the drawing:

Figure 1 is a perspective view of the upper portlon of the completecontact lighting unit; Figure 2 is 'a vertical sectional view throughthe lighting unit;

Figure 3 is an inverted plan view of the refractor; and

Figures 4, and 6 are fragmentary vertical sectional views through therefractor and taken on the planes 44, 5-5 and 6-6, respectively, ofFigure 3.

The metal base of the contact lighting unit is indicated at Hi. Itsupports in a manner not shown a concentrated filament lamp II. Anasrefracted toward the median plane 44, as in- E, F and G continues eachside of the plane 44 to approximately the position of ray 2!. Beyond therays 23 and the radial planes 24 the refracting power decreases. Beyondthe planes 24-24 the prisms are reversed and meet at a point slightlydisplaced from the plane 4- -4.

In the plane 4-4, as illustrated in Figure 4 of the drawing, the innersurfaces of the prisms B, C and D are in planes at right angles to theplane 44, so that light rays passing through this narrow area are notdeviated horizontally. As the radial prisms E, F' and G increase inrefracting power away from the plane 44 the slope of thesurface of theannular prisms B, C and D also changes. The new slopes at typicalplanes, such as H and 84, are indicated at B, C and D, and B", C" andD", respectively. In order to visualize this circumferential variationin slope of the inner surfaces of the refractor dotted lines are drawnin Figures 5 and 6 at the slope of the prisms in the plane 44 and aredesignated by reference characters b, c. d.

In the plane 4--4 the annular prisms act to bring the divergent lightreceived from the source and reflector into parallelism and emit it at aslight angle above the horizontal, as indicated by tragal ring I!carries straps l3 supporting a spherical reflector '4. The astragal ringi2 is clamped in place by an upper ring is and bolts it. The astragalring carries a cover plate I! and between the cover plate I! and the topof the ring i2 are carried suitable gaskets l8; l9 and a refractor 20.

The outer surface A of the refractor, as indiof the refractor is hereshown as being divided into three annular steps B, C and D, and each ofthe steps B, C and D is provided with radial prisms E, F and G. 4

The retracting power of the prisms E, F and G increases on each side ofthe median plane 44, so that light rays, such as 2i, 2: and 23, will be'cated in the vertical sections of Figures 2, 4, 5 v and 6, isexternally convex. The inner surface the rays 25, 25' in Figures 2, 3and 4. These rays suffer no lateral deviation. When the more and moredivergent rays from the source, such as rays 2|, :2, 23, are bent towardthe plane 4-4 by the laterally retracting prisms superposed on thesurface of the annular prisms and emitted by the sloping outer surfaceof the refractor, the lateral deviation tends to exaggerate the verticaldeviation of the annular prisms so that the light rays tend to be benttoward the ground. In order to compensate for this the vertical anglesof the inner surfaces of the annular prisms B, C and D are changed, asindicated in Figures 5 and 6. For example, the ray ii of Figures 3 and 5is at the same angle above the horizontal as the corresponding ray inFigures 2 and 4, but owing to the difference in slope of the surface Cthe vertical angle of the ray in glass is diflerent and this ray strikesthe external surface at still a dif-- a different vertical deviation atthe outer surface, so that the emergent ray 2! is also at substantiallythe same vertical angle as the rays 26'.

It will thus be seen that the collecting of the light through thedominant part of a semicircle about the unit into a beam projected in amedian direction and with substantially all the light at the same angleabove the horizontal is acconi plished by. a single refractor, which inthe present instance is externally smooth and convex and has annularprisms to produce vertical concentration and radial prisms superposed onthe inner surface of the annular prisms and having circumferentialvariation in retracting power to produce concentration incircumferential directions, and the annular prisms vary in depthcircumferentially with the greatest depth where the radial prisms havethe least refracting power and with the least depth where the radialprisms have,

a the greatest refracting power. The laterally acting prisms may be onthe outer surface.

Since it is obvious that the invention may be embodied in other iorrnsand constructions with- I in the scope of the claims, I wish it to beunderstood that the particular form shown is but one of these'forms, andvarious modifications and changes being possible, I do not otherwiselimit myself in any way with respect thereto.

What is claimed is:

1. A luminaire comprising a substantially point light source, an annularone-piece refractor accepting a. sector of an annular zone of divergentlight from the source and having annular prisms to produce concentrationin vertical directions and radial prisms superposed on the surfaces ofthe annular prisms and having circumferential variation in retractingpower to produce concentration in circumferential directions, theannular prisms varying in depth circumferentially with the greatestdepth where the radial risms have the least retracting power and withthe least depth where the radial prisms have the greatest retractingpower, so as to maintain substantially uniform, for all of said prisms,the vertical angle of the emergent light.

2. A luminaire comprising a substantially point light source, an annularone-piece refractor acceptlng a sector of an .annular zone of divergentlight from the source and having annular prisms to produce concentrationin vertical directions and radial prisms superposed on the innersurfaces of the annular prisms and having circumferential variation inretracting power to produce concentration in circumferential directions,

- the annular prisms varying in depth circumferentially with thegreatest depth where the radial prisms have the least refracting powerand with the least depth where the radial prisms have the greatestretracting power, .so as to maintain substantially uniform, for all ofsaid prisms, the vertical angle of the emergent light.

3. An externally smooth refractor annular about a normally vertical axisof smaller diameter at its top than at its bottom and externally convexin vertical planes, the inner surface of the refractor having aplurality of annular steps of decreasing steepness toward the top and ofdecreasing circumferential variation in steepness on opposite sides oi amedian vertical plane, said steps forming vertically acting prisms whichdepress rays from an axially disposed source below the bottom of therefractor and having formed thereon prismatic ridges ofcircumferentially varying retracting power which eil'ect concentrationtoward said median plane of light originating in said source.

THOMAS W. ROLPH.

